<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        body {
            height: 3000px;
        }

        .header {
            height: 100px;
            font-size: 33px;
            background-color: #b6db3c;
            line-height: 100px;
            text-align: center;
        }

        .content {}

        .item {
            background-color: #f2f4b2;
        }

        .item-a {
            font-size: 40px;
            background-color: #b03f0a;
            position: sticky;
            top: 0;
        }

        .item-b {
            font-size: 40px;
            background-color: #86b00a;
            position: sticky;
            top: 0;
        }

        .item-c {
            font-size: 40px;
            background-color: #0a7eb0;
            position: sticky;
            top: 0;
        }
    </style>
</head>

<body>
    <!-- 头部 -->
    <div class="header">header</div>
    <!-- 内容区域 -->
    <div class="content">
        <div class="item">
            <div class="item-a">A</div>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
            <h2>AAAA</h2>
        </div>
        <div class="item">
            <div class="item-b">B</div>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
            <h2>BBBB</h2>
        </div>
        <div class="item">
            <div class="item-c">C</div>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
            <h2>CCCC</h2>
        </div>
    </div>
</body>

</html>